The present invention relates to devices that dispense a volatile air treatment chemical by heating a chemical housed in a reservoir. It also relates to improved refills for use with such devices.
The prior art is replete with attempts to efficiently dispense air treatment chemicals such as insect control agents (insecticides, insect repellents, insect growth regulators, attractants, synergists, etc.), fragrances and deodorizers. See e.g. U.S. Pat. No. 6,551,560. The disclosure of this patent, and of all other patents referred to herein, are incorporated by reference as if fully set forth herein.
Conventional devices typically dispense a volatile air treatment chemical by heating a substrate on one side, thereby causing dispensing in an opposed direction. The heating source is typically an electrical heater.
A variety of air treating functions can be achieved with such devices. For example, a volatile insecticide can be dispensed in this way and then used to inhibit mosquito biting in a confined bedroom. Alternatively, a deodorizing or other odor control material can be dispensed to overcome malodors, or to simply provide a desired fragrance.
One problem with such devices is that the chemical to be dispensed, typically coated or impregnated on a porous substrate of some kind, usually rests against or near a heater. The heater heats the substrate, causing the volatized air treatment chemical to be driven off in a direction away from (essentially perpendicular to) a heater surface. See e.g. U.S. Pat. No. 4,228,124.
This can create some inefficiencies. For example, the portion of the material adjacent the heater can act as an insulator for the portion of the substrate which is releasing the active chemical, making control of the dispensing more difficult.
Another problem with such devices is that it may be difficult to determine when such a device is used up. Yet another problem relates to a lack of flexibility where multiple chemicals are to be dispensed which are optimally dispensed under different heating conditions.
Thus, there is a need for improved devices which address these problems.